<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<div id="app">
    <!--class类名中，用单引号括起来的，系统会当成字符串解析-->
    <h2 class="title" :class="['active', 'line']">{{message}}</h2>
    <!--class类名中，没有用单引号括起来的，是一个变量，系统会从script中传值-->
    <h2 class="title" :class="[active, line]">{{message}}</h2>
    <h2 class="title" :class="getClasses()">{{message}}</h2>
</div>

<script src="../../js/vue.js"></script>
<script>
    const app = new Vue({
        el: '#app',
        data: {
            message: '你好啊',
            active: 'aaaaa',
            line: 'bbbbb'
        },
        methods: {
            getClasses: function () {
                return [this.active, this.line]
            }
        }
    })
</script>

</body>
</html>